The Communication Workers' Union's postal executive has called a rolling series of strikes based on different sections of the workforce:

Mail centres (sorting offices): all shifts at or after 7pm on Wednesday 25 July until 7pm Thursday 26 July and all shifts at or after 3am Tuesday 31 July until 3am Wednesday 1 August.
Delivery offices: all shifts at or after 7pm Friday 27 July until 7pm Saturday 28 July and all shifts at or after 3am Thursday 2 August until 3am Friday 3 August.

Workers' Liberty's bulletin for the strikes - along with old bulletins, a "Support the postal workers" petition and other materials - can be downloaded at  http://www.workersliberty.org/node/8906